The last time this happened housing collapsed

A house, with its foundation washed away, hangs over a rain-swollen creek at Nyhammar in Dalarna, central Sweden.Reuters/Scanpix SwedenThe most expensive home listed for sale globally is in Bel Air, a neighborhood in Los Angeles. Its main house is a 74,000-square-foot monstrosity. Among the special attributes: a 30-car garage. The compound, being erected by speculative builder Nile Niami, has an asking price of $500 million.

Seven of the world's 10 most expensive listings are in the US. Four of them are in Los Angeles, including lesser abodes, such as a 38,000-square-foot mansion with a 5,300-square-foot master suite, several guesthouses, and staff housing, for $150 million.

Other countries have cool stuff for sale too, such as Pierre Cardin's 13,000-square-foot "Le Palais Bulles" ("the Bubble Palace") on the French Riviera, listed for about $450 million.

More supply of speculative super-homes is coming, including this gem, according to the New York Times: "Real estate agents and developers say a home under construction in Bel Air is likely to have more than 50,000 square feet of living space" and "the world's largest safe." It will be listed for "around $300 million."

For the first time ever, there are now officially 27 residences listed for sale globally with price tags above $100 million, according to Christie's International Real Estate. That's up 42% from last year, and up 125% from 2014!

Some super-priced homes are offered only privately, rather than through public channels, to avoid the hoopla that this sort of QE-wealth-effect creation brings. "Brokers say," according to the Times, that with those "whisper listings," the total "could easily top 40 or 50."

But last year, only two homes in that 9-figure price category actually sold, according to Christie's: a house in Hong Kong acquired by Alibaba's Jack Ma for $193 million, just as Hong Kong's housing bubble has begun to implode; and a townhouse in London that went for $132 million. In 2014, only five sold. In the prior three years combined, only eight sold. And now there are perhaps over 50 for sale….

How did we get here? Seven years of global QE and wealth effect, instigated by Ben Bernanke.

On Friday, he himself introduced Fed chair Janet Yellen to the audience. She then said that the Fed's bailouts and money-printing gyrations engineered by her predecessor during the Financial Crisis were "nothing short of magnificent." "Ben was immensely courageous," she said. "America owes him an enormous debt of gratitude."

So maybe "America" doesn't owe him that sort of gratitude, but the richest people in the world do. Their homes and other assets have shot up in price during Bernanke's reign when what he called the "wealth effect" had become official Fed policy.

When a regular guy sells a home for $200,000 that he bought for $100,000, he pockets a profit of $100,000 (less after fees and expenses) thanks to the housing "recovery" that the Fed's money printing caused. That's great for the regular guy. And it's not great for home buyers or renters. But when a not so regular guy sells a home for $100 million that had doubled in price, he walks away with a profit of $50 million.

That's how the "wealth effect" works. The more you have, the more you get. And the very top got by far the most. So yes, those folks owe Bernanke and now Yellen and all the other central bankers obsessed with QE, ZIRP, and NIRP, in Yellen's words, "an enormous debt of gratitude."

"It's just a new world in terms of what people are building and offering for sale" - that's how Dan Conn, chief executive of Christie's International Real Estate, explained the phenomenon to the Times.

Now these folks see the writing on the wall, and they figure it's a great time to sell, and so they put these things on the market to sell at peak wealth-effect prices, just when speculative builders are building and putting on the market even more nine-figure monuments. But there are apparently not a heck of a lot of buyers, and so these nine-figure homes for sale have piled up to record levels.

What might that mean? According to the Times: "Many say the sudden surge in hyperprice homes - often built and sold by speculative investors - is the ultimate bubble signal."

And when was the last time this sort of pile-up happened? In 2007 and 2008, just as the housing market was beginning to spiral down and as the Financial Crisis was beginning to mature. So now, the same signs are popping up once again.

While overall home prices were still soaring in the first quarter, at the top 5% of the housing market, the bubble has begun to deflate, with prices down 1.1%, according to Redfin. In some cities, the very top end is starting to take some hits, including in Manhattan where a luxury condo boom has turned into a glut, and where prices have begun to sag.